DSA is an established method for diagnostic viewing and quantitative assessment of neurovascular and peripheral interventional X-ray. Particularly, interventional imaging of heart and coronaries is an important field of application but a cardiac DSA revealing the contrast agent in the moving coronaries is not yet available for diagnostic viewing with sufficient quality or to enable subsequent quantitative coronary angiography (QCA).
In state of research and technology, for subtraction of an image in form of a diagnostic angiogram, a pre-captured image is selected sometimes referred as the mask image or mask that shows the heart in the same phase of the cardiac cycle and without contrast agent. The mask is then spatially deformed (warped) to compensate for residual motion to result in a subtraction image with as little subjective visual artifacts as possible.
A deformation vector field that results in best-possible matching of mask and angiogram is created and applied to the mask prior to subtraction.
The EP 0 840 253 relates generally to a method for X-ray imaging and, more particularly, to DSA for imaging vasculature. According to EP 0 840 253 a method for generating a DSA image from mask image data and opacified image data is described. The mask image is referred to as the X-ray image taken before injecting a contrast agent into the blood vessels. The opacified image is referred to as the X-ray image taken after injecting the contrast agent.
For patients with coronary heart disease, i.e. the target patient group of coronary angiography, irregularities in shape and dynamics of the heart beat—especially after injection of contrast agent—are observed. In consequence, available masks are not always sufficient to capture the contraction status of the heart in an angiogram frame and, therefore, provide a high-quality mask input. Even when single DSA frames are of high subjective visual quality, a discontinuity or wrap-around artifact is visible in a sequence of multiple heart beats whenever the end of the mask frame acquisition is reached and an earlier frame has to be selected for subtraction.
Thus, a high-quality coronary subtraction angiograph is important to allow for improved diagnostic viewing and to enable subsequent quantitative coronary angiography QCA.
There may be a need for an effective and a reliable method, which may be provided within a compact configuration and which may generate medical images, preferably DSA images, more accurately. Such accurate images should preferably have minimum artifacts due, e.g. to motion of the patient or its organs, and should be corrected for any misregistration changes from one part of the image to another part of the image.